[Ipopt] Homebrew formula for IPOPT on OSX

[Dominique Orban]

Interested Mac users will find my current IPOPT formula at [1]. The formula for MUMPS is at [2]. While I was at it, I added support for AMPL models via a formula for the ASL, available at [3].

The IPOPT formula generates both static and dynamic libraries. By default, the BLAS and LAPACK used are those from the Accelerate Framework. Optionally, users may select to build `--with-openblas` to use the OpenBLAS libraries. METIS (version 4) may also be used for ordering before factorization. No attempt yet on the Matlab interface.

Any comments or feedback on the formulae (or help with the Matlab interface) welcome.

Hopefully, this will all get pulled into Homebrew/Science soon.

Enjoy!

Dominique

[1] https://gist.github.com/7015914
[2] https://github.com/Homebrew/homebrew-science/pull/392
[3] https://github.com/Homebrew/homebrew-science/pull/393